It is known to use oxyalkylene-containing polymers as superplasticizers or water-reducers in concrete. For example, in U.S. Pat. No. 5,393,343, Darwin et al. disclosed “EO/PO” type comb polymers, containing ethylene oxide and/or propylene oxide groups, that were useful as superplasticizers for retaining “slump” (a property similar to the concept of flowability) in cement mortars and concretes over a sustained period of time.
Also known is the use of various agents for inhibiting the adverse effects of certain swellable clays, such as smectites and montmorrillonites, on the dosage-efficiency of such superplasticizers. These clays are sometimes contained in sand aggregates used for making mortar cement and concrete, and often cause poor workability in the fresh cement or concrete.
It was theorized that such clays expanded when initially wetted by the mix water, such that, in the expanded state, the clays absorbed or entrapped the superplasticizer. This in turn decreased the dosage efficiency because more superplasticizer would be needed to maintain the desired slump level in the hydrating cementitious composition, such as might be required for transporting the mix in a truck or pouring the mix at the construction site.
In U.S. Pat. Nos. 6,352,952 B1 and 6,670,415 B2, Jardine et al. (Grace Construction Products) first realized that this problem was caused by certain clays, and disclosed the use of various agents for preventing the clays from absorbing the superplasticizers, thus restoring dosage response. Such clay-activity-modifying agents included inorganic cations, organic cations, polar organic molecules capable of clay-absorption, clay dispersants such as polyphosphates, and mixtures thereof.
In the wake of Jardine et al., others in the industry began to focus on clay-inerting agents in cements. For example, in US 2007/0287794 A1, Alain et al. explained that cationic polymers, such as quaternary amines, were particularly appropriate for inerting clays. Along these lines, Japanese Patent application No. KOKAI 2006-45010 disclosed that a quaternary ammonium group, such as poly-diallyldimethylammonium chloride, could be used to increase effectiveness of the cement dispersant when in the presence of undesirable fine aggregates containing the problematic clay minerals.
The present inventors believe that the problems caused by clay-containing sands will increase in the cement and concrete industries due to a decline in the supply of high quality natural sand. Such sand aggregates will have a significant effect on the rheological and physical properties of mortars and concretes. The specific gravity, particle size distribution, shape and surface textures of the sand aggregate will influence the rheological properties of cement mortars and concretes in their plastic state; while the mineralogical composition, toughness, elastic modulus, and other properties of the aggregates will affect cement mortars and concretes in their hardened state.